JPH0880836A - Brake device of electric vehicle - Google Patents

Abstract

PURPOSE: To improve operability by generating braking force suitable for speed with simple constitution by making negative pressure to be generated by a negative pressure generating means variable according to the output of an electric motor to drive an electric vehicle. CONSTITUTION: A vacuum pump 17 to be connected to a master cylinder 13 through a flow passage 16 is driven with its output made variable by means of an electric motor 18, and when a brake pedal 11 is stepped on, a master cylinder 13 is operated through a push rod 12, and a brake mechainsm 14 is operated. At this time, the electric motor 18 is driven, and negative pressure by means of the vacuum pump 17 acts on the master cylinder 13, and the stepping force of the brake pedal 11 is assisted, and while a pressure sensor 19 detects negative pressure force to act on the master cylinder 13 through the passage 16 and conducts output to a comparator 22, a negative pressure command map 24 sets the command value of negative pressure on the basis of the speed signal 23 of the electric motor 18 and conducts output to the comparator 22. A controller 20 conducts the drive control of the electric motor 18 according to the increase/decrease value of the comparator 22.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an electric vehicle,
The present invention relates to a braking device for an electric vehicle having a booster for reducing the pedal effort and increasing the braking force.

[0002]

2. Description of the Related Art In recent years, regulations on toxic substances in exhaust gas discharged from vehicles equipped with an internal combustion engine have become stricter from the viewpoint of natural environmental problems. Therefore, many new technologies are being researched and developed to meet this regulation,
Electric cars are one of them. Then, in putting this electric vehicle into practical use, there are problems related to braking in addition to output, running distance, fuel consumption and the like.

That is, in a brake device used in a vehicle having an internal combustion engine, for example, a leading trailing brake is provided with two brake shoes inside a drum integrated with a wheel, and these two brake shoes are used as a wheel. It is configured so that it can be pressed against the inner peripheral surface of the drum by a cylinder. On the other hand, a master cylinder having a reservoir tank is connected to the brake pedal via a push rod, and a wheel cylinder is connected to the master cylinder via a brake hose.

Therefore, when the brake pedal is depressed, the piston in the master cylinder moves via the push rod against the spring, and the oil passage is cut off from the reservoir tank. Therefore, a certain pressure acts from the master cylinder toward the brake hose, and the wheel cylinder operates to press the brake shoe against the inner peripheral surface of the drum to perform the braking action.

By the way, in such a brake device,
Since a large braking force cannot be obtained only by the force of a human foot, a booster device such as a brake booster that boosts the pedaling force of the brake pedal by using the intake pressure of the engine is used. This brake booster is generally
It is installed between the brake pedal and the master cylinder, and it sucks the internal diaphragm by the intake pressure of the engine and pushes the push rod, which generates a force several times the pedal force of the human foot. Even if you step on it lightly, you can get a large braking force.

However, a booster such as a brake booster utilizing the intake pressure of the engine is applied to an internal combustion engine and cannot be applied to an electric vehicle that obtains a driving force by an electric motor. . Therefore, a vacuum pump driven by a dedicated electric motor is mounted, and this vacuum pump generates a negative pressure necessary for operating the brake booster.

[0007]

However, in the brake device applied to the above-mentioned conventional electric vehicle,
There is a problem that it is not possible to generate a braking force adapted to the speed of the vehicle. That is, in a brake device having a booster mounted on an internal combustion engine, the negative pressure required to operate the brake booster is the intake pressure generated in the intake stroke of the engine, and the magnitude of the intake pressure is the accelerator pedal. It is inversely proportional to the depression amount of and is proportional to the engine speed. Therefore, when the engine speed is low (during low speed traveling), the assisting force of the brake device is small and the braking force is small, and when the engine speed is high (during high speed traveling), the assisting force of the brake device is large. And a large braking force can be obtained.

On the other hand, in a brake device for an electric vehicle having a booster mounted on the electric vehicle, the vacuum pump is driven so that the negative pressure generated by the vacuum pump is maintained at a predetermined set value. Turn on / off electric motor
Have control. Therefore, although there is a power saving effect, the assisting force of the brake device becomes constant regardless of the vehicle speed,
If a predetermined set value of the negative pressure of the brake device is set so that the required braking force can be obtained when the vehicle is traveling at high speed, there is a problem that excessive braking force is generated at low speed traveling and the riding comfort is deteriorated. there were.

The present invention solves the above problems, and an object of the present invention is to provide a braking device for an electric vehicle, which can generate a braking force adapted to the speed of the electric vehicle even in the case of the electric vehicle. And

[0010]

A brake device for an electric vehicle according to the present invention for achieving the above object is a brake pedal, a master cylinder connected to the brake pedal via a push rod, and the master cylinder. A brake mechanism connected to the master cylinder via a brake hose, boosting means connected to the master cylinder to boost the pedaling force of the brake pedal, and negative pressure generating means connected to the boosting means. In a brake device for an electric vehicle, the negative pressure generated by the negative pressure generating means is variable according to the output of an electric motor for driving the electric vehicle.

A braking device for an electric vehicle according to the present invention includes a brake pedal, a master cylinder connected to the brake pedal via a push rod, and a brake mechanism connected to the master cylinder via a brake hose. A negative pressure generating means connected to the master cylinder for boosting a pedaling force of the brake pedal, and a negative pressure generating means connected to the boosting means. Has a first negative pressure generating means driven by an electric motor for driving the electric vehicle and a second negative pressure generating means driven by a power source different from the electric motor. One or both of the first negative pressure generating means and the second negative pressure generating means can be selectively driven according to the output of the electric motor. Is shall.

Further, in the brake device for an electric vehicle according to the present invention, the negative pressure generating means measures a negative pressure acting on the master cylinder, and a negative pressure measurement value measured by the pressure detecting means. Comparison means for comparing a negative pressure setting value set in advance according to the speed of the electric vehicle, and the first negative pressure generation means and the second negative pressure based on the judgment result of the comparison means. It is characterized in that either one or both of the generating means can be driven.

Further, in the brake device for an electric vehicle according to the present invention, the negative pressure generated by the negative pressure generating means is proportional to the output of the electric motor, and the output of the electric motor is zero.
Alternatively, when the output is very close to 0, a preset low output negative pressure value is set.

[0014]

In the brake system for an electric vehicle according to the first aspect of the present invention, when the brake pedal is depressed, the master cylinder operates via the push rod, and a constant pressure acts from the master cylinder toward the brake hose. Then, the brake mechanism operates and the braking force acts. At this time, the negative pressure generated by the negative pressure generating means acts on the boosting means to assist the brake pedal depressing force, and this negative pressure is variable according to the output of the electric motor for driving the electric vehicle. Therefore, a small assisting force acts at low speed of the vehicle, while a large assisting force acts at high speed of the vehicle.

In the brake device for an electric vehicle according to the second aspect of the present invention, when the brake pedal is depressed, the master cylinder operates via the push rod, and a constant pressure acts from the master cylinder toward the brake hose. Then, the brake mechanism operates and the braking force acts. At this time, the negative pressure generated by the first negative pressure generating means and the second negative pressure generating means acts on the boosting means to assist the brake pedal depression force. At times, a small assisting force acts by the negative pressure of only the first negative pressure generating means, while at the time of high speed of the vehicle, a large assisting force is generated by the negative pressure generated by both the first negative pressure generating means and the second negative pressure generating means. Power acts.

In this electric vehicle braking device, the pressure detecting means measures the negative pressure acting on the master cylinder, and the comparing means determines the negative pressure measurement value measured by the pressure detecting means and the speed of the electric vehicle in advance. The negative pressure setting means compares the negative pressure setting value set by the above, and the negative pressure generating means applies a small assisting force by the negative pressure of only the first negative pressure generating means while the vehicle is operating at a low speed based on the result of the determination. At high speed, a large assisting force is exerted by the negative pressure generated by both the first negative pressure generating means and the second negative pressure generating means.

Further, in the brake device for an electric vehicle, the negative pressure generated by the negative pressure generating means is proportional to the output of the electric motor, so that the assist force acts by the small negative pressure when the vehicle is low speed, and the high speed of the vehicle is high. Occasionally, a large negative pressure acts on the assisting force, and at the time of extremely low speed of the vehicle or when the vehicle is stopped, an appropriate assisting force acts on the preset low output setting negative pressure.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a brake device for an electric vehicle according to a first embodiment of the present invention.

The electric vehicle of this embodiment is constructed by connecting an electric motor to drive wheels via a transmission, and connecting a battery to the electric motor.
Therefore, the electric motor is driven by using the charged battery as a drive source, and the front wheels are rotated through the transmission, so that the vehicle can be driven to run.

In the brake system for an electric vehicle of this embodiment, as shown in FIG. 1, a master cylinder 13 is connected to a brake pedal 11 via a push rod 12, and the master cylinder 13 has a brake (not shown). The brake mechanism 14 is connected via a hose.
The master cylinder 13 is connected to a booster 15 that boosts the pedal effort of the brake pedal 11. In addition,
The brake mechanism 14 will not be described in detail, but
It may be any fluid-operated one, such as a leading / trailing brake or a disc brake.

In this booster 15, a vacuum pump 17 as negative pressure generating means is connected to the master cylinder 13 via a flow path 16, and the vacuum pump 17 can be driven by an electric motor 18. It is like this. Further, in this embodiment, the negative pressure generated by the vacuum pump 17 driven by the electric motor 18 is made variable according to the output of an electric motor (not shown) for driving the electric vehicle.

That is, a pressure sensor 19 is attached to the flow passage 16 connected to the master cylinder 13. On the other hand, a control device 20 for controlling the output of the electric motor 18 is connected to the electric motor 18 that drives the vacuum pump 17, and a comparator 22 is connected to the control device 20 via an output map 21. There is. A pressure sensor 19 is connected to the comparator 22, and a negative pressure command map 24 that outputs a negative pressure command value based on a speed signal 23 of an electric motor (not shown) for driving the electric vehicle is connected. Has been done.

When the brake pedal 11 is stepped on, the master cylinder 13 is actuated via the push rod 12, a certain pressure is applied from the master cylinder 13 to the brake hose, and the brake mechanism 14 is actuated. Braking force is applied. At this time, the electric motor 18 is driven, and the negative pressure generated by the vacuum pump 17 acts on the master cylinder 13 to assist the depression force of the brake pedal 11. Then, the pressure sensor 19 detects the negative pressure acting on the master cylinder 13 via the passage 16 and detects the negative pressure.
2, the negative pressure command map 24 sets a negative pressure command value based on the input speed signal 23 of the electric motor of the electric vehicle and outputs the command value to the comparator 22. Comparator 2
2 outputs the increase / decrease value from the set value of negative pressure and the detected value,
The control device 20 drives and controls the electric motor 18 according to the increase / decrease value.

Therefore, a small assisting force acts on the master cylinder 13 at low speed of the electric vehicle, while a large assisting force acts on the master cylinder 13 at high speed. When the detected value is larger than the set value of the negative pressure input to the comparator 22, the electric motor 18 is stopped by a limiter (not shown) in the control device 20.

As described above, in the braking system for the electric vehicle of this embodiment, the negative pressure acting on the master cylinder 13 to assist the pedaling force of the brake pedal 11 is supplied from the electric motor for driving the electric vehicle. By making it variable according to the speed signal, a small assisting force acts at low speed of the vehicle, while a large assisting force acts at high speed of the vehicle. The person can drive the vehicle without feeling discomfort.

FIG. 2 shows a schematic structure of a brake device for an electric vehicle according to a second embodiment of the present invention. It should be noted that members having the same functions as those described in the above-described embodiments are designated by the same reference numerals, and redundant description will be omitted.

In the brake system for an electric vehicle of this embodiment, as shown in FIG. 1, a master cylinder 13 is connected to a brake pedal 11 via a push rod 12, and the master cylinder 13 has a brake (not shown). The brake mechanism 14 is connected via a hose.
The master cylinder 13 is connected to a booster 25 that boosts the pedal effort of the brake pedal 11.

In this booster 25, a vacuum pump 26 as a first negative pressure generating means is connected to the master cylinder 13 via a flow path 16, and the vacuum pump 2
6 can be driven by an electric motor 27 for driving an electric vehicle. Further, a vacuum pump 28 as a second negative pressure generating means is connected to the flow path 16, and the vacuum pump 28 is driven by an electric motor 29 mounted separately from the electric motor 27 for driving the electric vehicle. It can be driven. In the present embodiment, only the vacuum pump 26 or only the vacuum pump 26 is output according to the output of the electric motor 27 of the electric vehicle.
Both the vacuum pumps 26 and 28 can be selectively driven.

That is, a pressure sensor 19 is attached to the flow passage 16 connected to the master cylinder 13. On the other hand, as described above, the electric motor 27 is connected to the vacuum pump 26, and the electric motor 2 that drives the vacuum pump 28.
A control device 20 for controlling the output of the electric motor 29 is connected to 9, and a comparator 22 is connected to the control device 20 via an output map 21. The pressure sensor 19 is connected to the comparator 22, and
A negative pressure command map 24 that outputs a negative pressure command value based on a speed signal 23 of an electric motor 27 for driving an electric vehicle is connected.

When the brake pedal 11 is stepped on, the master cylinder 13 is actuated via the push rod 12, a certain pressure is applied from the master cylinder 13 toward the brake hose, and the brake mechanism 14 is actuated. Braking force is applied. At this time, the electric motor 27 is driven, and the negative pressure generated by the vacuum pump 26 acts on the master cylinder 13 to assist the depression force of the brake pedal 11. Then, the pressure sensor 19 detects the negative pressure acting on the master cylinder 13 via the passage 16 and detects the negative pressure.
2, the negative pressure command map 24 sets a negative pressure command value based on the input speed signal 23 of the electric motor 27 of the electric vehicle and outputs the negative pressure command value to the comparator 22. The comparator 22 outputs the increase / decrease value from the negative pressure set value and the detected value, and the control device 20 outputs the electric motor 29 according to the increase / decrease value.
Is controlled to determine whether to operate or stop the vacuum pump 29.

Therefore, when the electric vehicle is at a low speed, the electric motor 27 for driving the electric vehicle is driven and a small auxiliary force acts on the master cylinder 13 by the negative pressure of only the vacuum pump 26, while at the time of a high speed, both electric vehicles are driven. The large assist force master cylinder 1 is driven by the negative pressure generated by the vacuum pumps 26, 28 driven by the motors 27, 29.
3 will be affected.

As described above, in the brake system for the electric vehicle of this embodiment, the vacuum pump 26 and the electric motor 27 driven by the electric motor 27 for driving the electric vehicle.
Vacuum pump 2 driven by an electric motor 29 different from
8 is provided and only the vacuum pump 26 or the vacuum pump 26 is provided depending on the speed signal from the electric motor 27 of the electric vehicle.
By selectively driving both the vacuum pump 28 and the vacuum pump 28, a small assisting force is exerted by the one vacuum pump 26 at a low speed of the vehicle, while a large assisting force is exerted by the two vacuum pumps 26, 28 at a high speed of the vehicle. Is applied, an unfamiliar braking force does not act during braking, and the driver can drive the vehicle without feeling uncomfortable.

FIG. 3 shows a schematic structure of a brake system for an electric vehicle according to a third embodiment of the present invention. It should be noted that members having the same functions as those described in the above-described embodiments are designated by the same reference numerals, and redundant description will be omitted.

In the brake system for an electric vehicle of this embodiment, as shown in FIG. 1, a master cylinder 13 is connected to a brake pedal 11 via a push rod 12, and a brake mechanism 14 is connected to the master cylinder 13.
Is connected. The master cylinder 13 is connected to a booster device 35 that boosts the pedal effort of the brake pedal 11. In this booster 35, a vacuum pump 26 is connected to the master cylinder 13 via a flow path 16, and the vacuum pump 26 can be driven by an electric motor 27 for an electric vehicle. In addition, the flow path 16
A vacuum pump 28 is connected to the vacuum pump 28, which can be driven by an electric motor 29.
In this embodiment, only the vacuum pump 26 or both the vacuum pumps 26 and 28 are selectively driven based on the negative pressure set value set according to the output of the electric motor 27 of the electric vehicle. I am free.

That is, a pressure sensor 19 is attached to the flow passage 16 connected to the master cylinder 13. On the other hand, a control device 20 for controlling the output of the electric motor 29 is connected to the electric motor 29 that drives the vacuum pump 28, and a comparator with hysteresis 32 is connected to the control device 20. And this comparator with hysteresis 3
A pressure sensor 19 is connected to 2 to input a measured negative pressure value, and a negative pressure set value set based on the speed of an electric motor 27 for driving an electric vehicle is input. Has become. In addition, 36 is the electric motor 2
A controller for an electric vehicle that controls the drive of 7, a transmission, and a differential device 38.

When the brake pedal 11 is stepped on, the master cylinder 13 is actuated via the push rod 12, a certain pressure is applied from the master cylinder 13 toward the brake hose, and the brake mechanism 14 is actuated. Braking force is applied. At this time, the electric motor 27 is driven, and the negative pressure generated by the vacuum pump 26 acts on the master cylinder 13 to assist the depression force of the brake pedal 11. Then, the pressure sensor 19 measures the negative pressure acting on the master cylinder 13 through the passage 16, and this negative pressure measurement value is input to the comparator with hysteresis 32.
A negative pressure set value set based on the speed of the electric motor 27 is input. The comparator with hysteresis 32 compares the negative pressure measurement value with the negative pressure setting value and outputs the increase / decrease value, and the control device 20 drives and controls the electric motor 29 according to the increase / decrease value to control the vacuum pump 29. Determine whether to activate or stop.

Therefore, when the electric vehicle is at a low speed, the electric motor 27 for driving the electric vehicle is driven and a small auxiliary force acts on the master cylinder 13 by the negative pressure of only the vacuum pump 26, while at the time of a high speed, both electric vehicles are driven. The large assist force master cylinder 1 is driven by the negative pressure generated by the vacuum pumps 26, 28 driven by the motors 27, 29.
3 will be affected. Further, since the driving of the electric motor 27 is stopped and the negative pressure by the vacuum pump 26 is not generated when the electric vehicle is at an extremely low speed or is stopped, the electric motor 29 is driven and the low output setting negative preset by the vacuum pump 28 is set. A pressure is generated, and an appropriate auxiliary force acts on the master cylinder 13 by the low output setting negative pressure.

As described above, in the braking system for the electric vehicle of this embodiment, the vacuum pump 26 driven by the electric motor 27 for driving the electric vehicle and the electric motor 27 are different from each other, as described above. The vacuum pump 28 driven by the electric motor 29 is provided, the comparator with hysteresis 32 compares the negative pressure measured value with the negative pressure set value, and the control device 20 drives and controls the electric motor 29 according to the increase / decrease value. By deciding whether to operate or stop the vacuum pump 29, a small assisting force acts on one vacuum pump 26 at a low speed of the vehicle, while a large assisting force is exerted on the two vacuum pumps 26, 28 at a high speed of the vehicle. In addition, the vacuum pump 28 applies an appropriate auxiliary force when the vehicle is operating at an extremely low speed or when the vehicle is stopped, and an unfamiliar braking force does not act during braking. The driver can be able to operate without discomfort a vehicle, obtaining a reliable braking force even during very low speed or stop of the vehicle.

[0040]

As described above in detail with reference to the embodiments, according to the brake device for an electric vehicle of the present invention, the negative pressure generating means is connected to the boosting means for boosting the pedaling force of the brake pedal, Since the negative pressure generated by the negative pressure generating means is made variable according to the output of the electric motor for driving the electric vehicle, a small assist force acts at low speed of the vehicle and a large assist force at high speed. Therefore, the braking force adapted to the vehicle speed can be generated with a simple structure to improve the operability of the brake mechanism, and the driver can obtain a good braking interval.

Further, according to the brake device for an electric vehicle of the present invention, the negative pressure generating means is connected to the boosting means for boosting the depression force of the brake pedal, and the negative pressure generating means is used for driving the electric vehicle. The first negative pressure generating means driven by the electric motor and the second negative pressure generating means driven by a power source different from the electric motor are used as the first negative pressure generating means, and the first negative pressure is generated according to the output of the electric motor of the electric vehicle. Since it is possible to drive either or both of the generating means and the second negative pressure generating means,
When the vehicle speed is low, a small assisting force is applied by the first negative pressure generating means, while when the vehicle is high speed, a large assisting force is applied by both the first negative pressure generating means and the second negative pressure generating means. The existing device can be used to generate a braking force adapted to the speed of the vehicle to improve the operability of the brake mechanism, and the driver can obtain a good braking interval.

Further, according to the brake device for an electric vehicle of the present invention, the negative pressure generating means has the pressure detecting means for measuring the negative pressure acting on the master cylinder and the negative pressure measurement value measured by the pressure detecting means. A first negative pressure generating means and a second negative pressure generating means based on a judgment result of the comparing means, the comparing means comparing the negative pressure setting value set in advance with the speed of the electric vehicle. Since either one or both of them can be driven, a small assisting force acts at low speed of the vehicle, while a large assisting force acts at high speed of the vehicle, and a braking force adapted to the speed of the vehicle is generated. The operability of the brake mechanism can be improved.

Further, according to the brake device for an electric vehicle of the present invention, the negative pressure generated by the negative pressure generating means is proportional to the output of the electric motor, and the output of the electric motor is 0 or an output very close to 0. In some cases, the preset low output negative pressure value was set, so when the vehicle is extremely low speed or stopped, the preset low output negative pressure will cause an appropriate auxiliary force to act, which is adapted to the vehicle speed. The braking force can be generated to improve the operability and safety of the brake mechanism.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a brake device for an electric vehicle according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a brake device for an electric vehicle according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a brake device for an electric vehicle according to a third embodiment of the present invention.

[Explanation of symbols]

 11 Brake Pedal 13 Master Cylinder 14 Brake Mechanism 15 Booster 17 Vacuum Pump 18 Electric Motor 19 Pressure Sensor 20 Control Device 22 Comparator 25 Booster Device 26, 28 Vacuum Pump 27, 29 Electric Motor 32 Comparator with Hysteresis 35 Booster apparatus

Claims (4)

[Claims] 1. A brake pedal, a master cylinder connected to the brake pedal via a push rod,
A brake mechanism connected to the master cylinder via a brake hose, a boosting unit connected to the master cylinder to boost the pedaling force of the brake pedal, and a negative pressure generating unit connected to the boosting unit. A braking device for an electric vehicle, comprising: a negative pressure generated by the negative pressure generating means, which is variable according to an output of an electric motor for driving the electric vehicle. 2. A brake pedal, a master cylinder connected to the brake pedal via a push rod,
A brake mechanism connected to the master cylinder via a brake hose, a boosting unit connected to the master cylinder to boost the pedaling force of the brake pedal, and a negative pressure generating unit connected to the boosting unit. In a braking device for an electric vehicle, the negative pressure generating means is driven by a power source different from the first negative pressure generating means driven by an electric motor for driving the electric vehicle. A second negative pressure generating unit is provided, and either one or both of the first negative pressure generating unit and the second negative pressure generating unit is selectively selected according to the output of the electric motor of the electric vehicle. A braking device for an electric vehicle, which is characterized by being drivable. 3. The brake system for an electric vehicle according to claim 2, wherein the negative pressure generating means measures a negative pressure acting on the master cylinder, and a negative pressure measurement measured by the pressure detecting means. And a negative pressure setting value preset according to the speed of the electric vehicle, the first negative pressure generating means and the second negative pressure generating means based on the determination result of the comparing means. A braking device for an electric vehicle, characterized in that either or both of the negative pressure generating means can be driven. 4. The brake system for an electric vehicle according to claim 1, wherein the negative pressure generated by the negative pressure generating means is proportional to the output of the electric motor, and the output of the electric motor is 0 or 0. A braking device for an electric vehicle, which has a preset low output negative pressure value when the outputs are close to each other.